role:* doesn't work

[NE2]

You can't use role:* to search for anything with a role (though -role: does work).

[stoecker]

Use child type:relation instead. This results in all elements which have a role (i.e. are relation members).

[NE2]

I mean searching for a nonempty role.

[jttt]

I think -role: is enough. * works only for '=' operator, no other operator supports it (ie name=* won't work either)